Sound insulating construction



April 20, 1937. J. PAGE l-:r AL

souNn INSULATING CONSTRUCTION Filed July 26, 1953 2 Sheets-Sheet 1 4. i w :fari I. i A

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April 20, 1937. J. PAGE ET AL 2,078,207

scum) INSULATING` CONSTRUCTION Filed July 26. 1955 2 Sheets-Sheet 2 f2? ventura;

Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE SOUND INSULATING OGNSTRUCTION Application July 26, 1933, Serial No. 682,194

l2 Claims.

This invention relates to improvements in sound-insulating construction and has particular relation to a type of structure for minimizing the transmission of sound between adjacent rooms,

5 compartments, telephone booths, and the like.

The invention has been particularly developed in connection with a sound-proof door, but is equally suitable for embodiment in fixed wall panels or sections which may be used to enclose 1U a room or other space on all sides or any part thereof.

In the provision of so-called sound-proof structures heretofore, it has been the general practice to use one type of construction for the iixed walls and another type of construction for the doors.

Difiiculty has been frequently encountered, however, as a result of the doors being far less effective in sound insulation than the xed portions of the walls, so that no matter how elcient the walls might be. a great deal of this eiiiciency would be destroyed by the transmission of sound through the doors. It is for this reason that the present invention has been first directed to the provision of an efficient sound-insulating door, as above indicated.

Another diiilculty which has been encountered in connection with sound-insulating door constructions of the prior art has resulted from the fact that such structures, while relatively eiil- :m cient in preventing the transmission of sound at some frequencies, have a Very poor eiilciency at certain particular frequencies. Such critical values of sound frequency occur in any construction wherein the door or other panel is of unitary 3;, construction so that the panel may vibrate as a whole. For example. sound-insulating doors built on the weight principle have a natural frequency of vibration, and sounds of that frequency, or near that frequency, will be trans- 40 mitted through such doors with relatively great ease.

It has been common practice in many cases to determine the efiiciency of a sound-insulating door or panel on the basis of its average sound 45 transmission loss over the entire range of sound frequencies which may be encountered. When rated in this manner, a panel may show a relatively high theoretical efciency by reason of the average transmission loss being increased by high su values over certain portions of the frequency range, while the value at a particular frequency or frequencies may be so low as to render the panel practically useless as an insulator against sound vibrations of such frequencies.

In the development of the present invention,

attention has been given not only to the obtaining of a high emciency on the above-described basis of rating, but to the elimination of poor results at any particular frequency or frequencies. In this connection another method of rating the 5 sound-insulating value oi doors and walls has been taken into consideration. This method is based upon the so-called minimum loudness reduction value of the door or wall. It is a more rigorous method of evaluating sound insulation l0 and in some respects gives a truer value of the actual eiliciency of the construction. It is now well understood that a given amount of sound energy has a varying apparent loudness to the human ear, depending upon the frequency. The l5 minimum loudness reduction rating is arrived at by weighting the transmission loss at each frequency, according to the response of the human ear at that frequency. The minimum loudness reduction is the lowest reduction valve over the 20 range of frequencies of sounds normally encountered.

By providing a construction in which a relatively high minimum loudness reduction is obtained, the structure will be highly effective as an insulator against sounds of any particular frequency, as well as sounds o! mixed frequencies. and will not be characterized by a low insulating value at any particular point in the fref quency range.

The primary object of the present invention, therefore, is to provide a construction which will be highly eiective in sound insulation over the entire range of sound frequencies which may be encountered.

A further object of the invention is to provide a construction which may be readily built in the form of doors, wall panels, or other structures, at a minimum of expense, and at the same time producing a pleasing appearance without excessive bulk or weight.

The above-indicated objects are accomplished, ln general, by the construction oi a door or other building element as a composite structure embodying two spaced panels oi' widely diil'erent natural frequencies oi vibration. One of the panels is made as rigid as possible, while the other panel is made with the maximum obtainable flexibility within practical limits. The two panels are separated by an internal air space of substantial thickness whereby a cushioning action is obtained in the transmission of vibrations from one panel to the other. Within this space a layer of sound-absorbing material is preferably,

although not necessarily, disposed to increase the cushioning action of the air space.

The use of two separated panels of widely different natural frequencies has been found to provide a degree of sound insulation over the entire range of audible frequencies normally encountered, which has hitherto been considered unattainable. This result is achieved by reason of the fact that, while a sound of a given audible frequency impinging upon one of the panels may cause that panel to vibrate to some extent at or near its natural audible frequency or frequencies, such audible frequency or frequencies are widely different from any natural audible frequency of the other panel and will not cause the latter to vibrate to any appreciable extent, even if transmitted thereto from the panel upon which the sound rst impinged. This condition occurs regardless of which oi the two panels the sound is initially incident upon, and therefore the composite structure provides an effective insulation against transmission of sounds of any frequencies in either direction.

The invention will be more fully understood, and other objects and advantages thereof will become apparent, from a consideration of the detailed description of a particular embodiment of the invention. as appearing hereinafter. taken in conjunction with the accompanying drawings forming a part hereof and illustrating such ernbodiment. In these drawings:

Figure 1 is a fragmentary elevational view of a portion of a wall in a room having therein a door embodying the invention, and indicating the section lines on which subsequent views are taken;

Fig. 2 is a broken vertical sectional View taken on the plane indicated by the line 2-2 in Fig. i;

Fig. 3 is a broken horizontal sectional view taken on the plane indicated by the line 3-3 in Fig. 1; and

Fig. 4 is an elevational view showing the interior construction of the door, taken on the planes indicated by the line 4 4 in Fig. 3 and having certain of the parts broken away to give a better illustration of the entire construction.

Referring to the drawings, Fig. l shows a door set in a frame or casing II and presenting to view one side thereof. comprising a panel I2. Upon reference to Figs. 2 and 3, it will be seen that the panel I2 consists of a relatively thin sheet of plywood or the like, covering the entire area of the door on one side. 'I'he opposite surface of the door is constituted by a composite wood veneer sheet I3 secured to the outer surface of a relatively thick wood panel I4 and projecting beyond the edges of the latter to extend over the entire area of the door on that side.

'I'he panel I4 preferably consists of a plurality of strips or boards of Balsa wood or other material having similar desired characteristics, glued together in edge-to-edge relation to prevent warping. The essential characteristics of this panel are relatively great stiffness in comparison to the panel I2. and low magnitude of response to irnpinging sound vibrations, particularly in the lower audible frequency range. Balsa wood has been found to be highly satisfactory for these purposes, although other woods or materials having the desired characteristics may also be used. The panel I4 is preferably veneered on its inner surface, as by the multiple layers of veneer i5, havingthe same dimensions as the panel I4.

In order to make the composite panel I3, I4, IS, hereinafter referred to asgthe panel I4, as rigid as possible. the same is provided with a reenIQrcao'raee-r ing framework suitably constituted by a plurality of structural iron members of high rigidity, such as angle irons. A suitable arrangement of such reenforcement is best illustrated in Fig. 4 and consists of vertically-disposed angle irons I6, II, and I8 and horizontally disposed angle irons I9, 20, and 2l, the members I8 and 2| being disposed at the top and bottom, respectively. of the panel I4 and there being a plurality of the members 20 disposed at spaced intervals intermediate the top and bottom of the panel.

The angle irons I8 and IB are disposed adjacent the hereinafter-mentioned stiles of the door at the vertical edges thereof and are, therefore. designated as the stile angles. The angle irons I9 and 2| are similarly disposed adjacent the hereinafter-mentioned top and bottom rails of the door and for this reason are designated as the top and bottom rail angles. The angle iron II is designated as the central stiffener angle and the plurality of angle irons 20 are referred to as transverse stifi'ener angles.

Each of said angle irons is disposed with one flange thereof lying in a plane parallel to the panel I4 and with the other flange thereof projecting from the surface of said panel covered by the veneer i6 toward the resilient panel I2 of the door. As shown in Fig. 3, the inside surface of the panel I4 is formed with rabbeted grooves along the vertical edges thereof to receive the base flanges of the stile angles I6 and I8. The depth of these grooves is such that exposed surfaces of these flanges are flush with the exposed surface of the inside veneer covering I5 of the panel. The rail angles I 9 and 2| and the transverse stiiiener angles 20 overlap these flanges and extend across the entire veneered surface I5 with their base flanges in contact therewith.

vEach of the angle irons 20 is formed with a slot 20a in its projecting ange, so that the central stiifener angle I'I may be inserted therein, as best shown in Fig. 3. Between the transverse angle irons the central stiffener angle Il is spaced from the veneered surface I5 by shims 22 which are preferably made of wood. These shims are of the same thickness as the base flanges of the transverse stifl'ener angles 20 so that they provide the same spacing of the angle iron II from the exposed veneered surface I5.

The top and bottom rail angles I9 and 2| are preferably of heavier stock than the intermediate transverse angle irons 20, and for this reason the vertical stiii'ener member II is crimped, as indicated at IIa, so that the ends thereof lie hush on the exposed surface of the base flanges of said rail angles.

In order to reenforce the transverse stiffener angles around the slots 20a in the projecting flanges thereof splice members 23 in the form of short sections of angle iron are provided.A Each of these splice members is formed with an L- shaped slot 23a in .one flange thereof to fit around the stfl'ener angle member I "I, and this slotted flange is placed adjacent the projecting ilange of the corresponding stifener member 2l) and secured thereto by means of bolts 24. The other flange of each of these stiffening splice members extends in a plane parallel to the base flange of the stiening angle irons 20. but is located beyond the edges of the projecting flanges of the members I1 and 20, as shown.

Each of the said several stiilening angle irons is firmly secured to the panel I4 by means of bolts 2l. 'Ihese bolts are provided with large flat heads 25a located in counter-sunk recesses in the outer surface of the core portion of the panel I4 and are inserted in suitably spaced holes through the panel vprior to application of the outer veneer covering II. The shanks of the bolts 2i are formed with short square portions 2lb of slightly enlarged diameter, adjacent the heads of the bolts, whereby the bolts are securely held against turning in the holes in the panel Il. As best shown in Fig. 4. a considerable number of the bolts are used, so that the reenforcing framework is secured to the panel il at frequent intervals. Certain of these bolts are located at points where two of the various angle irons overlap and the bolts thus located therefore serve to secure both such angle irons to the panel at those points.

The stile angle members ii and II are so located that the outwardly-presented surfaces of the projecting flanges thereof are flush with the edges of the core member of the panel il, and the rail angle members Il and 2i are similarly located with respect to the top and bottom edges of the core of the panel. The door construction includes a hinge stile 2B, a lock stile 21, and top and bottom rails 28 and 29. respectively. These mem- 7 bers are made of suitable wood, the lock stile 21 being of composite structure including portions 21a and 2lb, as shown. although it will be understood that this feature is optional and not essential to or connected with the invention.

'I'he door stiles and rails are arranged around the periphery of the core of the panel il, with the inner surfaces of said members abutting against the corresponding edges of said panel core and also against the outwardly-presented surfaces of the corresponding projecting angle iron flanges. These stiles and rails are glued to the portions of the veneer covering I3 which extend beyond the edges of the panel core i4 to the extreme edges of the door, and may also be glued to the edges of the core portion of the panel. They are securely fastened in the positions thus established by means of suitable bolts 3i). Il, 32. and 3l, which are placed at frequent intervals along the length of each of said members.

The heads of these bolts are located in counterbored recesses in each of the wood stiles and rails and are subsequently covered by wood plugs inserted in said recesses to present a finished exterior surface, as is customary. These bolts extend through aligned holes in the projecting flanges of each of the corresponding stile and rail angie members and are drawn up tight, to provide a rigid construction. The thin panel I2 is glued to the surfaces of the stile and rail members opposite those which abut against the veneered surface I3, and completes the external construction of the door itself.

Prior to the application of the thin panel I2, however, the inside surface of the panel Il (constituted by the veneer covering il) is preferably, although not necessarily, covered by pads of sound-absorbing or vibration-damping material 34, consisting of acoustical felt or other suitable material of similar characteristics. These pads are cut to the proper size to t in each of the rectangular spaces between adjacent angle irons and may be suitably secured to the panel il as by nails 35. The exposed surfaces of these pads are preferably covered with a layer of paper 36 which is cut in pieces of the same size as the pads and suitably attached to the edges of the latter.

The addition of the pads addsdamping to the cushioning effect oi' the air space within the door under certain conditions, and the addition of the flexible membrane covering of paper or the like has been found to provide a still further increase in the damping action in some cases.

When the above-described construction is embodied in a door, asin the particular embodiment of the invention herein shown and described, the same is hung on suitable hinges I1 in the usual manner. Since the construction does not involve unusually great weight, hinges and other hardware of ordinary design and size may be utilized.

Ahy desired type of knob or handle 38 may be provided and associated with any desired type of latching and locking mechanism. Itis preferable that a latch of the type which forces the door tightly into its closed position be utilized. but since such latches are well known and constitute no part of the present invention, this detail is not illustrated herein.

Gaskets l! are preferably carried by door stops 4U along both sides and the top of the door to prevent the passage of sound past these edges when the door is closed. and the bottom is preferably sealed in closed position by members Il of a so-called trigger bottom construction. 'I'hese members are automatically actuated by suitable mechanism upon closing of the door and are thereby caused to move downwardly and to press against th'e floor or threshold when the door is tightly closed, thus providing the desired sealing action at the bottom of the door. This construction likewise forms no part of the present invention and, being well understood in the art, is not shown or described in greater detail herein.

From the foregoing description. it will be seen that the present invention resides in a door or other wall panel or the like, which is of composite structure, comprising one panel of an extremely rigid nature and another panel of a very flexible nature. The two panels are separated by an air space of substantial thickness which provides a cushioning action to impede the passage of sound through the structure, and to this cushioning action may be added a damping eifect in some cases by the addition of pads of sound-absorbing felt or the like and further by lil the covering of the exposed surfaces of such pads i by membranes of paper or other flexible material. The most important and fundamental principle which is involved in the construction is the provision of the two panels having a wide difference in natural frequency of vibration and the separation of these panels in such manner that vibration of either one will be transmitted to the other to a minimum degree. Thus, the passage of any sound which may cause one of the panels to vibrate will be substantially completely prevented by the other panel, which has no natural period of vibration at or near the same frequency or frequencies.

While only one particular embodiment of the invention has been specitlcaliy shown and described herein, it will be apparent to those skilled in the art that various changes and modiilcations in the details of construction, arrangement of parts and general application of the invention may be made without departing from the spirit and scope of the invention, as set forth in the appended claims.

What is new and is desired to secure by Letters Patent. therefore, is:

1. A sound-insulating construction comprising a panel of high rigidity. a panel of high flexibility in comparison to said tlrst panel. means supporting said panels in spaced, parallel relation. and a layer of vibration-damping material covering the inside surface o! the rigid panel but only partly filling the space between said panels.

2. A sound-insulating construction comprising a panel of high rigidity, a panel of high dexibility in comparison to said first panel, means supporting said panels in spaced, parallel relation, a layer of vibration-damping material covering the inside surface of the rigid panel but only partly lling the space between said panels, and a flexible membrane extending over the exposed surface of said vibration-damping material.

3. A sound-insulatingconstruction comprising a panel of high rigidity, a panel' of high lleidbility in comparison to said first panel. means supporting said panels in spaced, parallel relation, a layer of vibration-damping material covering the inside surface of the rigid panel but only partly filling the space between said panels, and a flexible membrane extending over the exposed surface of said vibration-damping material and secured thereto.

4. A sound-insulating construction comprising only two spaced, parallel impervious panels rigidly supported at their peripheries and reenforcing means secured to the inner surface of one of said panels and rendering the same highly rigid, the other of said panels being relatively flexible and so mounted as to be free to vibrate over its entire unsupported surface.

5. A sound-insulating construction comprising spaced, parallel impervious panels rigidly secured to a supporting framework at their peripheries and structural iron reenforcing members secured to the inner surface of one of said panels and rendering the same highly rigid, the other of said panels being relatively iiexible and so mounted as to be free to vibrate over its entire unsupported surface.

6. A sound-insulating construction comprising spaced, parallel panels and a plurality of angleiron members secured at frequent intervals to the inner surface of one of said panels in intersecting relation to each other to render said panel highly rigid, the other of said panels being relatively exible and so mounted as to be free to vibrate over its entire unsupported surface.

7. A sound-insulating construction comprising spaced, parallel panels, a plurality of angle-iron members secured at frequent intervals to the inner surface of one oi said panels in intersecting relation to each other to render said panel highly rigid, the other of said panels being relatively iiexible, and rail and stile members supporting said panels in said spaced relation and secured to the reeni'orcing members along the corresponding edges of the rigid panel.

8. A sound-insulating door construction comprising spaced, parallel panels, a plurality of angle-iron members secured at frequent intervals to the inner surface of one of said panels in intersecting relation to each other to render said panel highly rigid, the other of said panels being relatively flexible, rail and stile members supporting said panels in said spaced relation and secured to the reenforcing members along the corresponding edges of the rigid panel, a casing for the door, and means for sealing the edges of the door in the casing to prevent the passage of sound around said edges.

9. A sound-proof door comprising a frame, and impervious panels rigidly supported thereby, one of said panels being relatively thick and rigid and hence resonant only to sounds of high audible frequency, the other panel being thin and ilexible and hence resonant only to sounds of low audible frequency, each panel having one side exposed to the spaces divided by the door, said flexible panel being free to vibrate over its entire unsupported surface.

l0. A second-proof door comprising a frame, and impervious panels rigidly supported thereby, one of said panels being relatively thick and rigid and hence resonant only to sounds of high audible frequency, the other panel being thin and exible and hence resonant only to sounds of low audible frequency. each panel having one side exposed to the spaces divided by the door, anda layer of sound-absorbing material between said panels and in contact with the rigid panel, said thin panel being free toV vibrate over substantially its entire unsupported surface.

il. A sound-proof door construction comprising a rigid frame having impervious panels rigidly secured thereto, one of said panels being substantially rigid and iniiexible, and the other being of a highly flexible nature and free to vibrate over its entire unsupported surface.

l2. A sound-proof door construction comprising a rigid frame, a rigid impervious panel rigidly secured within the frame substantially flush with one surface thereof, and a relatively thin and flexible impervious panel rigidly secured to the marginal portions of said frame on the side opposite to that Where the rigid panel is secured, said thin panel being free to vibrate over substantially its entire unsupported surface.

JOHN PAGE. GEORGE W. BAKER.

'CERTIFICATE oF coRREcTIoN.

Patent No. 2,078,207. April 2o, 193'?.

JOHN PAGE, Er AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4. second column, line 27, claim 10, for second-proof" read sound-proof; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

4Signed and sealed this 29th dey of June, A. D. 1937.

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

